F150 Transmission Problems

Check the level of the transmission fluid by using the dipstick. The level should only be checked when the fluid is warm; the fluid is generally considered warm after the vehicle has been driven 20 miles. Over-filled and under-filled conditions can cause transmission problems

Since 1988, F150s have had an electronic engine control (EEC) system that feeds data to an on-board computer. The computer instructs the transmission when to shift. If the computer or a part of its signal network fails, the transmission may shift hard or not shift at the right time.

Check the engine idle speed and general performance. If the engine is not running properly, you need to resolve any problems before resuming the transmission diagnostics. There are several sensors attached to the engine that feed data to the on-board computer; misinformation from these sensors can cause problems that appear to be transmission-related.

Externally, the only adjustments that are possible for the home mechanic are to the shift linkage. Older models (pre-1991) have a shift rod that connects to the bellcrank. The rod can be disconnected at the frame and pried out of the manual control lever for adjustment or replacement. Newer models use a shift cable; adjusting the tension on this cable is critical and requires two people.

If there are no easily spotted problems, then the malfunction is probably due to a mechanical failure. Mechanical failures can range from a worn gear that causes slipping to a broken band that prevents the driver from shifting into reverse. Due to their complexity, mechanical problems should be referred to a trained mechanic to resolve.